JUNCTION FIELD EFFECT TRANSISTOR (JFET)
A Junction Field Effect Transistor (JFET)
is a three
device in which current conduction is by one types
perature ror making differ
making ditterent ypes ol thermistors. Electrical connections
after pressuring the surfa
Figure – 17
As shown in the Figure-17, thermistors are made in the shape of beads,
hes up to 25 mm dlameter and rods trom-6 mm to 50 mm long. Beads may
alass-coated or enclosed in evacuated envelopes for protection against
Pl Temperature/ Kesistance curve : Figure-18 shows curve of Resistance
Temperature, it 1s seen that the thermistor has a resistance of about 3000 2
at -20C and 40 at 80°C.
change ot 100 °C has resulted ina
75:1 change in resistance. It causes
very large change in resistance which
makes a thermistor such a valuable
control device. There are two ways of
changing the resistance of the device
nternally and externally. Device
temperature and self-heating
18) pplications Thermiste find many applicat1ons some of which are given
For neasrement and control of temperature as in ovens,
Figure – 18
other electronic devices
18 Ilow rate measuring devices
- For regulating ac voltage
GFor liquid level detection e
Characteristics The 1-V
characteristic of a solar cell 1s a
plot betwveen output voltage and
output current for different
ntensities of incident light.
It is shown in the Figure-16.
Consider the characteristic for
the incident light intensity of
a0 40 60 80 100 120 140 160 180
maximum and equals 10x
If the circuit is on urrent
output voltage is maximum and equals 0.4 Volt.
zero, power output is again zero.
the cell must be operated at the knee of the curve.
Application of Solar cell: